Human hookworm infection is a leading cause of malnutrition and anemia in the less developed nations of the tropics, with an estimated I billion individuals infected by these parasites. There is an urgent need for a vaccine against hookworm because of the failure of conventional anthelminthic drugs to control this parasitic disease. The Biomedisyn Corporation in collaboration with scientists from the Yale Medical Helminthology Laboratory have cloned and expressed a promising vaccine antigen known as rASP-1. This molecule is immunogenic in experimental animals and stimulates immune responses which are similar to those identified with early live attenuated larval vaccines. Unlike live larval vaccines, however, rASP-1 is potentially suitable for immunizing human populations at risk for acquiring hookworms, as well as related nematode infections in the U.S., such as toxocariasis and strongyloidiasis. We propose to compare expression of soluble rASP-1 in a model eukaryotic system with our E.coli- derived rASP-1 in order to produce antigen that conformationally resembles the native molecule. We will then compare the immunogenicity and the ability of rASP-1 to protect mice against challenge infections with the third-stage, infective larvae of Ancylostoma. These studies will lay a foundation for a human vaccine against ancylostomiasis. PROPOSED COMMERCIAL APPLICATION: The rASP-1 antigen has the potential to be the basis for a recombinant vaccine for human hookworm and related nematode infections in the U.S., including hookworm infection among military personnel, children with toxocariasis, and immunocompromised patients with strongyloidiasis. This molecule and its derivatives may also be used -as vaccines for nematode infections of livestock.